Booster Motor

[Terry1]

I have a Coleman DGAA056BDTA furnace. Symptoms are as follows:
Thermostat calls for heat, I hear humming in the booster/combustion motor but it does not spin. I read 120vac going into the two terminals of the motor. After opening the small door and manually spinning the fan blade, it still does not spin when power is applied. The fan blade spins with no obstruction, and apparently is connected to the motor shaft since I get the "magnetic" effect of "locking into place" as you slowly spin the blade. Again, the motor is humming so it's apparently not an open primary winding.

So my question is do you think the problem could be anything but a bad motor? I'm about to order a replacement booster assembly but thought I'd bounce it off an expert.

If I temporarily jumper across the pressure switch, the burner lights and immediately goes out, which from what I'm reading is probably because the flame is starved for oxygen with no booster motor running, and it doesn't remain long enough to kick in the flame sensor.

One final confusion for me is that when I first tried the furnace this season, the 2 trouble flashes are indicating a closed pressure switch, even though a meter shows it's open. Hope this doesn't mean I could also have something going on with the main board. I can't think of a reason that the booster motor would not run as long as there's 120vac going to it so I'm assuming the best thing would be to start by replacing the booster assembly and see where I go from there.

Thanks for an expert's input!

Terry

[Terry1]

Well, the problem was, indeed, the booster motor. I got a replacement assembly, installed it, and the furnace works again.

Terry

[Mark]

Glad you got it figured out.

Mark